Five American tours in, it’s hard to believe Glasvegas have waited this long to finally visit their half-namesake city. The black-clad Scottish foursome – either still hungover or still drinking after last night’s club bender – have been in Las Vegas for barely 24 hours. There’s no time to take it easy and no place to hide any wobbles, though: tonight’s gig, a ‘secret’ show sponsored by MySpace inside the tiny Viva Las Vegas Wedding Chapel, will be streamed online and kicks off the band’s longest US jaunt to date. It also serves as a taster show for when the band swing back this way for a proper gig on the Strip. Proper, in that no matter which venue Glasvegas play, it’ll be nothing like tonight’s one. Oh, apart from the cemetery they’re playing in a few days.

Once onstage, the band, surveying both the setting and the crowd of roughly 100 before them, seem more alert than earlier alcohol intake would suggest. “We gonna have a good time?” asks James Allan from underneath a mammoth stained-glass window. Glasvegas play up to the theme, with Caroline McKay decked out in a wedding dress behind her simple drumkit and James out front in a dark, crisp blazer and sunglasses. He sings demurely at first, barely matching the fervour of cousin Rab’s guitar during opener ‘Geraldine’. But when the second verse hits, James projects his voice high above the torrent of noise.

For the next 45 minutes, Glasvegas assume the roles of bride, groom, minister, organ player and wedding band simultaneously. The interior loses much of its kitsch factor thanks to the strategic, and oddly holy, positioning of the lights and the potency of the band’s performance. But there’s no room for an altar, as Marshall amp stacks flank the band, blasting out full-throated anthems (‘Flowers And Football Tops’) and poignant power ballads (‘It’s My Own Cheating Heart That Makes Me Cry’) alike; for a place designed more for consorts than concerts, the sound is remarkably pristine. The local witnesses, perhaps initially expecting little more than a publicity stunt, are clearly impressed.

And yet, the staging and room still play second to the band, specifically to Allan’s juxtaposed mix of Strummer-like cocksureness and a Springsteen-esque everyman air. Takeaway moments abound. When he sings, “Remember times when you put me on your shoulders?” during ‘Daddy’s Gone’, a young boy is hoisted atop his father at the back of the audience. For most of ‘Go Square Go’, James sings from under his mic, except when he and the crowd chant the song’s famous “Here we fucking go!” refrain (which ought to replace ‘what happens in Vegas stays in Vegas’ as Sin City’s marketing slogan). He starts ‘Flowers…’ with a sing-song apology about his band’s no-show at April’s Coachella festival in nearby Palm Springs: “I fell asleep/And missed the whole fucking thing!” Not to worry: Glasvegas have plenty of opportunities ahead in this part of the world as the band heavily tour here over the next two months. A pre-gig chat also reveals that not only is James currently writing new material – though sadly none makes tonight’s setlist – but he plans to set up camp in Los Angeles to record these new songs. For now, though, the honeymooning Glasvegas are eager to consummate their new union with Las Vegas – and the rest of America.